Clamp circuits have been used in a number of prior art circuits. They may also be considered snubber circuits which limit a voltage across a circuit element. In DC to DC converter circuits, semi-conductor switches are used to control the flow of energy. When the switch is opened an inductance is in the circuit, such as a transformer primary, a high voltage is generated across the switch as it turns off. The prior art clamp circuits have in some cases used a capacitor in circuit across the semi-conductor switch, perhaps with a diode in circuit therewith but also a resistor feeding power back to the input voltage source. This resistor dissipates energy rather than positively utilizing that energy.
The U.S. Pat. No. 3,297,960 to Massey, shows a converter which uses a pair of diodes 1 and 2 to prevent saturation of a transistor 3 by maintaining a near zero voltage across the base and collector. The diodes are connected directly to the secondary of the power transformer to provide current and voltage feedback. Massey does not show the energy storage configuration of the present invention.